Nucleotide-Induced Conformational Changes in Tetrameric GroEL Mapped by Hydrogen/Deuterium Exchange

GroEL is a large (molecular weight ≈ 800,000) protein complex composed of two heptamers arranged like stacked doughnuts. By “spray-painting” the complex with heavy water, and then cutting into pieces with an enzyme and weighing the pieces, we are able to map the solvent accessibility throughout the complex, and observe conformational changes induced by binding of an analog of adenosine triphosphate (ATP), thereby illuminating the mechanism by which ATP activates the complex for its biological function.